Humidity responsive switch



Nov. 16, 1954 s. w, NICKELLS 2,694,757

HUMIDITY RESPONSIVE SWITCH Filed July 5, 1952 INVENTOR.

STANLEY W. N ICKELLS A T TOR/VE Y United States Patent O HUMIDITY RESPQNSIVE SWITCH Stanley W. Nicltelis, St. Louis Park, Minm, assignor to Minneapolieffoneyweli Regulator Company, Minneapolis, Mirna, a corporation of Delaware Application July 5, 1952, Serial No. 297,343

4 Claims. (Cl. 20061.06)

The present invention is directed to a humidity responsive switch and more particularly to the linkage employed for interconnecting the humidity responsive element and the switch per se.

An object of the invention is to provide a humidity responsive control device employing a unitary snap switch of the precision type actuated by a hair element.

Another object is to provide a linkage interconnecting a humidity responsive element and a snap switch that is capable of transmitting relatively high force with a minimum of friction loss and with a minimum of lost motion in order to obtain the desired results of accuracy of control and low operating differential.

A further object is to provide a pivotal mounting for a lever particularly adapted for actuation of a snap switch by a hair type humidity responsive element acting in tension.

Other objects will be evident from the specification and claims and from the drawing, in which:

Figure 1 is a view of a humidity responsive switch suitable for wall mounting, with its cover removed,

Figure 2 is a fragmentary view taken on line 22 of Figure l, and

Figure 3 is a fragmentary view taken on line 33 of Figure 2.

A frame is secured to a wall plate 11 in a manner that permits its removal to facilitate installation. A screw 12 holds the lower end of the frame to the wall plate and its removal permits disengagement of fastening means, not shown, between the upper part of the frame and the wall plate.

A unitary snap switch 15 of the self return type is secured to the frame 10 by screws 16. The switch 15 is of the type disclosed in McGall 1,960,020 and its internal construction will not be described here. It is provided with electrical terminals 17 and a translatable actuating button 18.

A bell crank lever 20 has an arm 20a, shown in Figures 2 and 3, that engages the switch actuating button 18, and an arm 20b to which a hair type humidity responsive element 21 is attached. The frame 10 is provided with an outwardly extending portion 10a having at flat surface lying in a plane normal to the path of movement of the button 18, and a pair of flexible reeds 22 and 23 are secured against this surface by rivets 24 and a backing plate 25. The reeds 22 and 23 extend on opposite sides of the arm 20b and are secured against a flat surface of the arm 20a by rivets 26 and backing plate 27. The reeds 22 and 23 are joined together at their ends, and, in effect, the arm 20a extends through an opening in the strip of which the reeds are formed.

A pair of ears 20c and 20d are bent away from the surface of arm 20a to which the reeds are attached and are bent again toward the plane including that surface and form a pair of aligned knife edges 20@ and 20] (see Figure 2) engaging the reeds 22 and 23. It will be noted that a free length of the reeds 22 and 23 separates the knife edges and the surface of arm 20a engaged by the reeds.

The fiat surface of the frame portion 10a to which the reeds 22 and 23 are attached terminates immediately beyond the knife edges 20a and 20f to provide a curved surface adjacent the knife edges. The protruding frame portion 10b serves to stiffen the portion 10a and assures proper alignment thereof adjacent the knife edges. Frame portion 10a is bifurcated to provide an opening to ac- 2,694,757 Patented Nov. 16, 1954 commodate arm 20b of the bell crank lever, and this opening is continued into frame portion 1012.

It will be noted that the frame portion 10b is shaped to provide free lengths of the reeds 22 and 23 intermediate the knife edges and the arm 20a of the bell crank'lever.

Since the reeds-22 and 23 are not laterally supported intermediate the knife edges and their engagement with the arm 20a of the bell crank lever, the pivotal axis for the bell crank lever is established by the knife edges 20a and 20] which are in alignment and bear on a plane surface established by the frame portion 10a. For convenience, the knife edges engage surfaces of the reeds 22 and 23, but it is within the scope of the invention that the device could be constructed with the knife edges directly engaging a surface of the frame, and in the described construction it may be considered that the por tions of the reeds so engaged actually are a part of the frame.

A frame portion 10c extends laterally from portion 10a and serves to protect the hair element 21 when the cover is being removed or applied. Another frame portion 10d (appearing only in Figure 1) extends outwardly from the frame as a further protection for the element 21 and additionally serves to strengthen the frame.

The upper end of the element 21 is adjustably supported on the frame 10, and is carried on an ear 30a on a lever 30 which is pivotally supported on a pin 31 secured to the frame 10. A spring 32 interconnects a portion 30b of lever 30 and an arm 102 of the frame, and biases the lever into engagement with a pin 33a carried on an adjusting lever 33 which is pivoted in the frame 10 on a pin 10 Suitable friction means, not shown, is employed to maintain the lever 33 in adjusted position. A mark on the upper end of the lever 33 cooperates with indicia of per cent relative humidity on the upper extremity of the frame 10. An eccentric 34 is provided on the lever 33 to relatively position the ear 33a to calibrate the device.

The wall plate 11 may be secured to a vertical conduit outlet box, or for low voltage wiring, may be attached directly to a wall. An opening 34 is provided in plate 11 adjacent the switch terminals 17 to accommodate the wiring. A cover, not shown, may be held at its upper end on the portion of the frame 11 hearing the indicia, and is secured to the frame at its lower end by a cover screw 35.

Other embodiments of the invention will be apparent to those skilled in the art and the scope of my invention is to be limited only by the appended claims.

I claim as my invention:

1. In a humidity responsive device, a base, a switch of the self return type carried by said base and having an actuator movable with respect thereto, a humidity responsive element, means for adjustably positioning one end of said element on said base, a lever one portion of which overlies a portion of said base, another portion engages said actuator and a third portion is connected to said element, and a laterally flexible reed interconnecting said lever and said base and serving as a lateral abutment between said base and said lever, said lever and said base being formed to provide a free length of reed therebetween not laterally engaged by either said base or said lever, said element and said lever being disposed so that said reed is placed in tension when force is applied to said actuator.

2. In a humidity responsive device, a base, a switch carried by said base, said switch having an actuator movable with respect to said base, a humidity responsive element, means for adjustably positioning one end of said element on said base, a bell crank lever interconnecting the other end of said element and said actuator, said base having a fiat surface portion disposed substantially normal to the path of movement of said actuator, a spaced pair of reeds interconnecting the flat surface portion of said base and a flat surface portion of said bell crank lever with a free length therebetween, said bell crank lever having a pair of laterally disposed portions shaped to avoid the free length of said reeds and to engage portions of said reeds lying along the flat surface portion of said base to establish the pivotal axis for said bell crank ever.

3. In a humidity responsive device, a base, a unitary 3. 1 snap switch of the self return type on said base, said switch having an actuator translatable with respect to said base, a hair element disposed normal to the path of movement of said actuator, means for adjustably positioning one end of said element on said base, a bell crank lever interconnecting the opposite end of said element and said actuator, said base having a flat surface portion parallel to said element and normal to the path of movement of said actuator, and a flexible reed attached to the fiat surface portion of said base with a first portion of said reed lying along said surface portion and a second portion extending beyond and free of said surface portion, said bell crank lever being attached to the free portion of said reed and having a pair of laterally disposed knife edge abutments engaging portions of said reed lying along said surface portion of said base.

4. In a humidity responsive device, a base, a laterally resilient strip attached rigidly to a portion of said base, a member secured to a portion of said strip removed from said base, said member having an extension engaging said base but avoiding the free length of said strip between said base and said member to form a pivotal axis for said member in said base, a hair element adjustably attached at one end to said base and having its other end connected to said member, said element being generally parallel to said strip but displaced therefrom, and a snap switch carried on said base and having an actuator engaged by a portion of said member, said actuator producing a force on said member substantially at right angles to the force due to said element, the resultant of the element force and the switch actuator force being in a direction to place said strip in tension and to cause said extension of said member to bear against said base.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 1,151,814 Norwood et a1 Aug. 31, 1915 1,237,470 Carrier Aug. 21, 1917 2,289,108 Eaton July 7, 1942 2,320,535 Peterson June 1, 1943 2,482,206 Pratt Sept. 20, 1949 

